answer and explanation
we are given initial values of temperature, pressure and volume as well as the final value of temperature and pressure and we are asked to find the final volume.
we can do this using the combined gas equation
P1V1/T1 = P2V2/T2
when we plug in the values we get:
(6atm x78L)/53K = (85atm x V2/17K
8.83 = 85atm x V2 / 17K
V2 = 1.77 Liters